JP5050417B2 - Vehicle steering control device - Google Patents

Description

  The present invention belongs to the technical field of a vehicle steering apparatus capable of controlling the steered angle of a steered wheel regardless of a driver's steering operation.

In the conventional vehicle steering control device, the turning angle when the vehicle is in the straight traveling state is stored, and the steering actuator is controlled so that the stored turning angle is obtained when the steering handle is in the straight traveling operation state. Thus, when the steering wheel is in the straight running operation state, the straight running state of the vehicle is maintained. Specifically, the turning angle when the detected yaw rate or lateral acceleration of the detected vehicle is equal to or less than a predetermined value (≈0) is stored, and the stored turning angle is added to the target turning angle as an offset angle. Thus, the shift amount in the traveling direction of the vehicle when the steering wheel is in the straight traveling operation state is corrected (for example, see Patent Document 1).
JP 2000-62633 A

  However, in the above prior art, the offset angle is set with respect to a steady amount of deviation caused by the difference between the left and right air pressures of the wheels, so that the vehicle goes straight due to a transient road surface disturbance or a side wind. When the vehicle is in an incapable state, it is not reflected in the stored offset angle, and therefore cannot be dealt with, and there is a problem that the driver is forced to perform a steering operation to maintain a straight traveling state.

  The present invention has been made to solve the above problems, and the object of the present invention is to maintain a straight traveling state of a vehicle without forcing a driver to perform a steering operation against a transient disturbance input to the vehicle. An object of the present invention is to provide a vehicle steering control device.

In order to achieve the above object, in the present invention,
In a vehicle steering device that can control the steering angle of a steered wheel regardless of the driver's steering operation,
A turning behavior detecting means for detecting a yaw rate or a lateral speed;
Integrating means for calculating the yaw angle or lateral displacement by integrating the yaw rate or lateral velocity;
A steering angle correction amount that cancels the yaw angle or lateral displacement calculated by the integrating means after the vehicle is in a straight traveling state after the vehicle is in a straight traveling state until the driver's steering intervention is made. A turning angle correction amount calculating means for calculating,
A turning angle correction means for correcting the turning angle based on the turning angle correction amount;
It is characterized by providing.

  In the vehicle steering control device according to the present invention, the traveling direction is corrected so that the vehicle travels straight after the vehicle enters the straight traveling state until the driver's steering intervention is performed. It is possible to maintain a straight traveling state of the vehicle without forcing the driver to perform a steering operation in response to a disturbance input.

  Hereinafter, the best mode for carrying out the present invention will be described based on Examples 1 and 2.

First, the configuration will be described.
FIG. 1 is a configuration diagram of a steer-by-wire (SBW) system to which a vehicle steering control device according to a first embodiment is applied. The SBW system according to the first embodiment includes a steering handle 1, a steering angle sensor 2, and a reaction force motor. 3, backup clutch 4, steering motor 5, steering angle sensor 6, steering mechanism 7, front wheel (steering wheel) 8, reaction force controller 9, steering controller 10, and communication line 11. And. The reaction force motor 3 and the steering motor 5 are configured by, for example, a brushless motor or the like.

  In the SBW system of the first embodiment, the steering handle 1, the front wheel 8 and the steering mechanism 7 are mechanically separated. However, the backup clutch 4 is provided as a backup means, and when any abnormality occurs in the SBW system, the backup clutch 4 is fastened and the steering handle 1 and the steering mechanism 7 are mechanically connected. Safe driving is possible.

  In the first embodiment, the steering motor 5 is driven so that the target turning angle according to the operation state of the steering handle 1 is obtained, and at least the target steering reaction torque corresponding to the steering state of the front wheels 8 is applied. SBW control for driving the reaction force motor 3 is performed.

The steered controller 10 calculates the command current value of the steered motor 5 and drives the steered motor 5 so that the actual steered angle of the front wheels 8 matches the commanded steered angle.
The reaction force controller 9 calculates a command current value of the reaction force motor 3 based on the turning angle of the front wheel 8 detected by the turning angle sensor 6 and drives the reaction force motor 3. The reaction force controller 9 calculates a target turning angle based on the rotation operation amount (steering angle) of the steering handle 1 detected by the steering angle sensor 2.

  Further, in the first embodiment, variable gear control is performed in which the ratio of the turning amount of the front wheels 8 to the steering handle 1 is variable according to the vehicle speed or the like. In this variable gear control, for example, the ratio of the actual steering angle with respect to the steering wheel angle is increased in the extremely low vehicle speed range to reduce the steering burden such as the stationary steering, while the actual steering angle with respect to the steering wheel angle is increased in the high vehicle speed range. Control is performed such as reducing the angle ratio to improve straight running stability.

[Turning angle correction logic]
FIG. 2 is a turning angle control system block diagram showing turning angle correction logic in the turning controller 10 of the first embodiment.

  In the first embodiment, when a yaw angle or a lateral displacement (deviation amount) is generated from a straight traveling state due to road disturbance or a side wind, a command current value for driving the steered motor 5 in a direction to suppress the deviation amount is determined, and the front wheels The steering angle of 8, 8 is corrected.

  As a correction method, first, a deviation amount in the traveling direction of the vehicle after the vehicle goes straight is calculated. As a calculation method, the integrator 10a is used to use a yaw angle that is an integral value of the yaw rate of the vehicle or a lateral movement amount that is an integral value of the lateral speed of the vehicle. The lateral speed can be obtained from each wheel speed. Also, the lateral movement amount can be obtained from lane detection, navigation information, etc. without using the integrator 10a.

  In the vehicle model 10b, the yaw angle or the lateral movement amount is input, and the turning angle of the front wheels 8 and 8 at which the input yaw angle (or the lateral movement amount) is generated is output as a correction amount. The comparator 10c calculates the corrected target turning angle by subtracting the correction amount from the target turning angle.

  The controller 10d outputs a command current value corresponding to the corrected target turning angle to the turning motor 5. Here, the controller 10d can use known gain control, PID control, and other control methods.

  Here, when the turning angle is being corrected, if the driver determines that the vehicle is not in a straight traveling state due to the steering angle, the steering angular velocity, or the steering torque, or the vehicle speed is equal to or lower than the determination threshold value, and no correction is necessary. When the vehicle speed is reached, the correction is interrupted. At that time, the amount of deviation is reset, but if the correction amount of the turning angle is reset, the target turning angle will change suddenly. Start correction from quantity.

  During the correction of the turning angle, the reaction force controller 9 is based on the value obtained by removing the change in the turning angle corresponding to the correction amount from the turning angle of the front wheel 8 detected by the turning angle sensor 6. By generating the steering reaction force, the fluctuation of the steering reaction force accompanying the correction of the turning angle is prevented.

[Turning angle correction control processing for straight running]
FIG. 3 is a flowchart showing the flow of the turning angle correction control process executed by the turning controller 10 of the first embodiment. Each step will be described below (corresponding to the turning angle correction means). This control process is repeatedly executed at a predetermined control cycle.

  In step S1, it is determined whether or not the absolute value of the steering angle is smaller than a predetermined value a. If YES, the process proceeds to step S2, and if NO, the process proceeds to step S7. Here, the predetermined value a is a steering angle in the vicinity of the neutral position where the vehicle can be determined to be in a straight traveling state.

  In step S2, it is determined whether or not the absolute value of the steering angular velocity is smaller than a predetermined value b. If YES, the process proceeds to step S3. If NO, the process proceeds to step S7. Here, the predetermined value b is a steering angular velocity at which the driver can determine that the steering angle of the steering wheel 1 is maintained constant.

  In step S3, it is determined whether or not the absolute value of the steering force (steering torque) is smaller than a predetermined value c. If YES, the process proceeds to step S4. If NO, the process proceeds to step S7. Here, the predetermined value c is a steering torque at which it can be determined that the steering handle 1 is near the neutral position.

  In step S4, it is determined whether or not the vehicle speed is greater than a predetermined value (determination threshold value) d. If YES, the process proceeds to step S5. If NO, the process proceeds to step S7. Here, the predetermined value d is a speed (for example, 60 km / h) at which it can be determined that the vehicle continues traveling straight, such as an expressway, and is traveling at a high speed causing a shift in the traveling direction. In step S4, based on lane detection, navigation information, etc., it is determined whether or not the vehicle is traveling on a straight path, and if the vehicle is traveling on a path other than the straight path, the process proceeds to step S5. If the vehicle is traveling on a curve, it may be set to proceed to step S7.

  In step S5, it is determined whether or not the correction flag F is 1. If YES, the process proceeds to step S10, and if NO, the process proceeds to step S6.

  In step S6, the counter is counted up and the process proceeds to step S7.

  In step S7, it is determined whether or not the count value of the counter is greater than or equal to a predetermined value T. If YES, the process proceeds to step S8. If NO, the process proceeds to step S1. Here, the predetermined value T is a time during which it can be determined that the driver is willing to drive the vehicle straight.

  In step S8, the count value of the counter is cleared, and the process proceeds to step S9.

  In step S9, the correction flag F is set to 1, and the process proceeds to step S10.

  In step S10, correction of the turning angle of the front wheels 8 and 8 is started, and the process proceeds to return. The correction amount of the front wheels 8 and 8 is calculated based on a deviation amount in the traveling direction of the vehicle after the vehicle is in a straight traveling state calculated from the yaw angle or the lateral movement amount of the vehicle.

  In step S11, it is determined whether or not the correction flag F is 1. If YES, the process proceeds to step S12. If NO, the process proceeds to step S13.

  In step S12, the correction flag F is set to 2, and the process proceeds to step S14.

  In step S13, it is determined whether or not the correction flag F is 2. If YES, the process proceeds to step S14. If NO, the process proceeds to return.

  In step S14, the previous correction amount is held, and the process proceeds to return.

Next, the operation will be described.
[Vehicle running state maintaining action]
On a straight road such as an expressway, when the steering wheel must always be operated in order to move the vehicle straight, it is troublesome for the driver and the operability is deteriorated. In the technique described in Japanese Patent Laid-Open No. 2000-62633, the turning angle when the vehicle is in the straight traveling state is stored, and the steering is performed so that the stored turning angle is obtained when the steering handle is in the straight traveling operation state. By controlling the actuator, the straight traveling state of the vehicle is maintained when the steering wheel is in the straight traveling operation state. Specifically, the turning angle when the detected yaw rate or lateral acceleration of the detected vehicle is equal to or less than a predetermined value (≈0) is stored, and the stored turning angle is added to the target turning angle as an offset angle. Thus, the shift amount in the traveling direction of the vehicle when the steering wheel is in the straight traveling operation state is corrected.

  However, in this prior art, the offset angle is set with respect to a steady amount of deviation caused by the difference between the left and right air pressures of the wheels, so that the vehicle cannot go straight due to a transient road surface disturbance or a side wind. In such a case, the stored offset angle is not reflected and cannot be handled. Therefore, the driver has to return the vehicle to the straight traveling state by his / her steering operation, and the operability is not improved so much.

  On the other hand, in the vehicle steering control device of the first embodiment, the amount of deviation in the traveling direction of the vehicle with respect to the straight traveling direction is obtained after the vehicle enters the straight traveling state and before the driver's steering intervention is performed. By correcting the target turning angle so as to eliminate the amount, the vehicle is prevented from deviating from the straight direction.

  That is, in the flowchart of FIG. 3, when the driver starts a steering operation to advance the vehicle straight during high speed travel, step S1 → step S2 → step S3 → step until the count value of the counter reaches a predetermined value T. The flow from S4 → step S5 → step S6 → step S7 is repeated.

  When the count value reaches the predetermined value T, the process proceeds from step S7 to step S8 → step S9 → step S9 → step S10, and thereafter, until the driver finishes the steering operation for moving the vehicle straight, step S1 → Step S2 → Step S3 → Step S4 → Step S5 → Step S6 → Step S7 → Step S8 → Step S9 → Step S10 is repeated, and the turning angle is corrected according to the amount of deviation in the direction of travel relative to straight travel Is done.

  Further, in the first embodiment, when a steering intervention is performed by the driver during the correction of the turning angle, the correction of the turning angle is ended and the previous correction amount is held. That is, from any step of step S1, step S2 or step S3, the process proceeds from step S11 to step S12 to step S13 to step S14, and thereafter, until the driver starts a steering operation for moving the vehicle straight again. Meanwhile, the flow of going from step S1 (or one of step S2 and step S3) → step S11 → step S13 → step S14 is repeated, and the correction amount is held.

  For example, when the correction of the turning angle is terminated by the driver's steering intervention, if the correction amount is set to zero, the target turning angle may change suddenly and the vehicle behavior may become unstable. On the other hand, in the first embodiment, by holding the previous correction amount, it is possible to avoid a sudden change in the target turning angle when the correction is interrupted.

In the first embodiment, the deviation amount is calculated based on the yaw angle of the vehicle or the lateral movement amount of the vehicle.
By calculating the amount of deviation based on the yaw angle, which is the integral value of the yaw rate, it is possible to detect the amount of deviation caused by the turning motion of the vehicle accompanying disturbance input from the road surface.
By calculating the amount of deviation based on the amount of lateral movement, it is possible to accurately detect the amount of deviation caused by the lateral movement of the vehicle due to the lateral wind.

In the first embodiment, in steps S1 to S3, it is determined whether or not the vehicle is in a straight traveling state based on the steering state (steering angle, steering angular velocity, steering torque).
For example, when determining the straight traveling state of the vehicle based on the detected vehicle behavior such as the yaw rate or the lateral acceleration, the straight traveling state of the vehicle can be determined only after a change in the actual vehicle behavior occurs. The start of correction will be delayed.

  On the other hand, in the first embodiment, whether or not the vehicle is in a straight traveling state is determined based on the steering state. Therefore, the vehicle behavior that changes according to the steering state is actually changed. This can be detected at a stage before the turning, and the turning angle can be corrected without delay.

  At the same time, in steps S1 to S3, the driver's steering intervention is determined based on the steering state. In particular, by determining steering intervention based on the steering angular velocity (step S2) and steering torque (step S3), early determination of steering intervention is possible, and the correction of the turning angle can be interrupted quickly. It can be avoided that the turning behavior is disturbed with the continuation of the steering angle correction.

  In the first embodiment, when the vehicle speed exceeds a predetermined value (determination threshold value) d in step S4, the turning angle is corrected based on the deviation amount. However, when the vehicle speed is equal to or less than the predetermined value d. , Do not make corrections. In other words, it is required to keep going straight when traveling on a highway or the like where straight running continues and a deviation in the direction of travel occurs, and it is necessary to keep going straight in general urban areas. Not. Therefore, by correcting the turning angle according to the vehicle speed, it is possible to achieve both correct correction of the turning angle during high-speed traveling and avoidance of unnecessary correction during urban driving.

  Further, in the first embodiment, in step S4, when the vehicle is traveling on a straight path, the turning angle is corrected based on the deviation amount. However, when the vehicle is not traveling on the straight path, the correction is performed. Do not implement. In other words, it is necessary to maintain straight travel when traveling on a straight road, and when traveling on a curve, it is not necessary to maintain straight travel. Therefore, by correcting the turning angle based on the road shape, it is possible to achieve both the reliable correction of the turning angle on a straight road and the avoidance of unnecessary correction during curve traveling.

  FIG. 4 is a time chart showing the straight travel state maintaining operation of the first embodiment. At time t1, the driver starts a steering operation to travel the vehicle straight during high speed travel, and thus the correction of the turning angle is started. As a result, once the vehicle goes straight ahead, steady disturbances such as road surface cants and transient disturbances such as road surface inputs and crosswinds are input to the vehicle until the driver intervenes in steering. Even if it is a case, the straight-ahead state of a vehicle is maintained.

  At time t2, since the steering intervention by the driver has been performed, the correction is finished, and the previous correction amount is held until time t3 when the driver starts the steering operation to advance the vehicle again. As a result, a sudden change in the target turning angle is avoided, and instability of the vehicle behavior can be suppressed.

Next, the effect will be described.
In the vehicle steering control device according to the first embodiment, the following effects can be obtained.

  (1) In a vehicle steering device that can control the turning angle of the front wheels 8 and 8 regardless of the driver's steering operation, after the vehicle goes straight, until the driver performs steering intervention The turning angle correction means (FIG. 3) is provided for correcting the turning angle based on the amount of deviation in the traveling direction of the vehicle after the vehicle is in a straight traveling state (step S10). Thereby, it is possible to maintain the vehicle in a straight traveling state without forcing the driver to perform a steering operation with respect to disturbance input to the vehicle.

  (2) When the driver's steering intervention is made, the turning angle correction means holds the correction amount based on the deviation amount (step S14), so that a sudden change in the target turning angle can be avoided and the vehicle behavior is unstable. Can be suppressed.

  (3) Since the turning angle correction means calculates the amount of deviation based on the yaw rate of the vehicle, the amount of deviation caused by the turning motion of the vehicle accompanying disturbance input from the road surface can be detected.

  (4) Since the turning angle correction means calculates the amount of deviation based on the amount of lateral movement of the vehicle, it is possible to accurately detect the amount of deviation caused by the lateral movement of the vehicle due to the lateral wind.

  (5) The turning angle correction means determines whether or not the vehicle is in a straight traveling state based on the steering state, so that the vehicle behavior that changes according to the steering state is actually changed. It can be detected at the previous stage, and the turning angle can be corrected without delay.

  (6) When the vehicle speed exceeds the predetermined value d, the turning angle correction means corrects the turning angle based on the amount of deviation. It is possible to avoid unnecessary correction.

  (7) When the vehicle is running on a straight road, the turning angle correction means corrects the turning angle based on the amount of deviation. Thus, it is possible to avoid unnecessary corrections.

  The second embodiment is an example in which the steering angle correction amount based on the deviation amount is gradually decreased when the driver's steering intervention is performed.

  The overall configuration is the same as that of the first embodiment shown in FIG.

[Turning angle correction control processing for straight running]
FIG. 5 is a flowchart showing the flow of the turning angle correction control process executed by the turning controller 10 of the second embodiment. Hereinafter, each step will be described (corresponding to turning angle correction means). In addition, the same step number is attached | subjected to the step which performs the process same as Example 1 shown in FIG. 3, and description is abbreviate | omitted.

  In step S21, the correction amount is gradually decreased from the previous correction amount, and the process proceeds to step S22. Here, the amount to be reduced is set to such an extent that the driver does not feel a change in the correction amount.

  In step S22, it is determined whether or not the correction amount is zero. If YES, the process proceeds to step S23, and if NO, the process proceeds to return.

  In step S23, the correction flag F is set to zero, and the process proceeds to return.

[Decrease in correction amount]
In the second embodiment, when steering intervention is performed by the driver during the correction of the turning angle, the correction of the turning angle is ended and the correction amount is gradually decreased. That is, in the flowchart of FIG. 5, the flow from step S1, step S2, or step S3 to step S11 → step S12 → step S21 → step S22 is repeated until the correction amount becomes zero. It is.

  For example, when the correction of the turning angle is terminated by the driver's steering intervention, if the correction amount is set to zero, the target turning angle may change suddenly and the vehicle behavior may become unstable. On the other hand, in Example 2, the sudden change of the target turning angle when the correction is interrupted can be avoided by gradually reducing the correction amount. Moreover, the uncomfortable feeling given to the driver can be suppressed by gradually reducing the correction amount.

  FIG. 6 is a time chart showing the straight traveling state maintaining action of the second embodiment, and the section from the time point t1 to the time point t2 is the same as that of the first embodiment, and thus the description thereof is omitted.

  At time t2, since the steering intervention by the driver has been performed, the correction is finished, and the correction amount gradually decreases until time t3 when the driver starts the steering operation for moving the vehicle straight again. As a result, a sudden change in the target turning angle is avoided, and instability of the vehicle behavior can be suppressed.

Next, the effect will be described.
In the vehicle steering control device of the second embodiment, in addition to the effects (1) and (2) to (7) of the first embodiment, the following effects can be obtained.

  (8) The steering angle correction means (FIG. 5) terminates the correction of the steering angle and gradually decreases the correction amount of the steering angle based on the deviation when the driver's steering intervention is made. A sudden change in the target turning angle can be avoided, and instability of vehicle behavior can be suppressed.

(Other examples)
The best mode for carrying out the present invention has been described based on the first and second embodiments. However, the specific configuration of the present invention is not limited to the first and second embodiments. Design changes and the like within a range not departing from the gist are included in the present invention.

  For example, in the first and second embodiments, the steer-by-wire system in which the steering handle and the front wheels are mechanically separated has been described. However, the vehicle steering control device according to the present invention is a steered wheel regardless of the driver's steering operation. As long as the steering angle can be controlled, the present invention is also applicable to a steering device in which a steering wheel and a front wheel are mechanically connected.

  In the first and second embodiments, the example of correcting the turning angle of the front wheels has been described. However, in the case of a vehicle having a mechanism for changing the turning angle of the rear wheels, the turning angle of the rear wheels, or the front and rear It is good also as a structure which correct | amends the steering angle of each wheel. When correcting the turning angles of the front and rear wheels together, it is possible to eliminate both the deviation amount based on the yaw angle and the deviation amount based on the lateral displacement amount, thereby further suppressing the deviation amount in the traveling direction with respect to the straight traveling direction of the vehicle. Is possible.

1 is a configuration diagram of a steer-by-wire system to which a vehicle steering control device of Embodiment 1 is applied. It is a turning angle control system block diagram which shows the turning angle correction logic in the turning controller 10 of Example 1. FIG. It is a flowchart which shows the flow of the turning angle correction | amendment control processing performed with the turning controller 10 of Example 1. FIG. 3 is a time chart illustrating a straight traveling state maintaining operation of the first embodiment. It is a flowchart which shows the flow of the turning angle correction | amendment control processing performed with the turning controller 10 of Example 2. FIG. 6 is a time chart illustrating a straight traveling state maintaining operation of the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering handle 2 Steering angle sensor 3 Reaction force motor 4 Backup clutch 5 Steering motor 6 Steering angle sensor 7 Mechanism 8 Front wheel 9 Reaction force controller 10 Steering controller 10a Integrator 10b Vehicle model 10c Comparator 10d Controller 11 Communication line

Claims (4)

In a vehicle steering device that can control the steering angle of a steered wheel regardless of the driver's steering operation,
A turning behavior detecting means for detecting a yaw rate or a lateral speed;
Integrating means for calculating the yaw angle or lateral displacement by integrating the yaw rate or lateral velocity;
A steering angle correction amount that cancels the yaw angle or lateral displacement calculated by the integrating means after the vehicle is in a straight traveling state after the vehicle is in a straight traveling state until the driver's steering intervention is made. A turning angle correction amount calculating means for calculating,
A turning angle correction means for correcting the turning angle based on the turning angle correction amount;
A vehicle steering control device comprising: The vehicle steering control device according to claim 1,
The steering angle correcting means determines whether or not the vehicle is in a straight traveling state based on a steering state. The vehicle steering control device according to claim 1 or 2 ,
When the vehicle speed exceeds a determination threshold, the turning angle correction means corrects the turning angle based on the turning angle correction amount. The vehicle steering control device according to any one of claims 1 to 3,
The steered angle correcting means corrects the steered angle based on the steered angle correction amount when the vehicle is traveling on a straight path.

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